swift: Generate a mmc ext4 tar image file

Swift has an emmc chip, add the directive to generate a tarball for it.

(From meta-ibm rev: 42c34123c54d5ebe407fbd7b87cc5ae6c75624a5)

Change-Id: I263399cba325131be2d72d9ae2d3015050317d8f
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-ibm/meta-witherspoon/conf/machine/swift.conf b/meta-ibm/meta-witherspoon/conf/machine/swift.conf
index 3915e2b..4c0abb5 100644
--- a/meta-ibm/meta-witherspoon/conf/machine/swift.conf
+++ b/meta-ibm/meta-witherspoon/conf/machine/swift.conf
@@ -1,6 +1,6 @@
 require conf/machine/witherspoon.conf
 
-IMAGE_FSTYPES += "ext4"
+IMAGE_FSTYPES += "ext4 mmc-ext4-tar"
 
 KERNEL_DEVICETREE = "${KMACHINE}-bmc-opp-${MACHINE}.dtb"